Questions about 1.1.3 Jailbreak and the iPod touch...

Hi iPod Touch fans!
I have a quick question regarding the NateTrue jailbreak...

1. I know it installs the iPhone firmware on the touch... How does that play with iTunes? Can it easily be restored back to the default 1.1.3 firmware for the touch (ie: it's not going to be an iphone forever, right?)

2. Will a January Software Upgrade remain intact? Can it be reinstalled if the touch is restored to an unjailbroken 1.1.3 touch?